To monitor an optical communication operation in an optical communication network, the optical communication network is provided with an optical power monitor (for example, see patent literature 1). The optical power monitor is, for example, built into an optical communication device, detects a power of an optical communication signal, and provides information on the detected power to a controller in the optical communication device.
Included as one example of the optical communication network is a WDM (wavelength-division multiplexing) network. At a branching point of the WDM network, for example, as the optical communication device, a ROADM device is disposed. The ROADM device is provided with an optical switch for switching the optical communication signal to any path and/or branching/inserting the optical communication signal. The optical power monitor is, for example, mounted to this ROADM device and is used to control an optical amplifier in the ROADM device and transmit the optical communication signal at an optimal power. Additionally, the optical power monitor is also used in an optical communication device such as an optical transceiver or an optical transponder that sends/receives an optical communication signal to control and/or monitor the power of the optical communication signal.